Story Highlights

Colts at Chiefs, 4:35 p.m. Saturday, NBC

INDIANAPOLIS – Marlon Mack has become something unstoppable in his second season with the Indianapolis Colts, a stick of dynamite with the fuse burning, the explosion coming. But that’s not why he’s better than he was a year ago.

Mack isn’t better because he can go 20 yards in the flap of a hummingbird’s wings. He could always do that, back in high school in Sarasota, at college at South Florida, even as a rookie with the Colts. If that’s why you think he’s better, after he gained 908 yards in 12 regular-season games, after becoming the first Colt since Joseph Addai in 2007 with four 100-yard games in one season, after breaking the franchise record with 148 rushing yards in the playoff victory against the Houston Texans, well, you’re thinking too big.

Think about what he did to the Dallas Cowboys, and no, not the whole picture. Not that he became the first back with 100 yards (he had 139) and two TDs against the Cowboys in four years. You’re thinking too big again.

Think smaller. Think about the Colts’ first drive. Second-and-4 at the Cowboys 8. Handoff to Mack. Dallas safety Xavier Woods grabs him at the 7 and goes for a ride – think: water skier, doing the slalom – to the 1. First down.

Now it’s third-and-goal. Still at the 1. Another handoff. Mack collides with Dallas safety Jeff Heath, spinning off him and into the end zone. The touchdown caps a drive Mack began with a 19-yard run, trucking Cowboys cornerback Chidobe Awuzie at the line, putting down his left hand for balance and roaring onward.

That’s the eyeball test that suggests Mack has gotten better, and the advanced statistics confirm it. Before I give you those numbers behind Mack’s improvement, let me give you the reasons.

He wouldn’t talk about the shoulder

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Training camp in July was our first look at Mack since Colts General Manager Chris Ballard had revealed earlier in the offseason that Mack had played all of 2017 with a torn labrum. And then had surgery.

Someone asked Mack for clarification: What was the injury?

“It was my shoulder,” he said. “I can’t remember right now.”

Was it your labrum?

“Yeah,” he said, “I think so. I’m not too sure.”

Mack didn’t want to talk about it. This week, I asked him why.

“I didn’t want to make it an excuse,” he says. “I still went on the field and played.”

Yes, but. You needed surgery.

Says Mack: “I won’t say it was a big impact. I just felt it, put it like that.”

He’s the same stick of dynamite he always was, but now the fuse burns on short-yardage plays, too. Plays like these two in the regular season finale at Tennessee, a game the Colts won 33-17 to reach the playoffs as Mack ran 25 times for 119 yards:

Third quarter. Handoff to Mack. Titans 6-2, 252-pound linebacker Harold Landry hops on his back at the line of scrimmage – think: piggyback – and Mack carries him 5 yards. Also third quarter. Another handoff to Mack. He has gained all of 1 yard when he lowers that shoulder and explodes into safety Kevin Byard, pushing him, dragging him another 5 yards.

The Colts offensive line loves this.

“It’s just been so fun,” center Ryan Kelly was saying a few weeks ago, when Mack was in the middle of this current rampage, “him running behind us.”

In the last four games – three the Colts had to win to reach the playoffs, then at Houston – Mack has had 88 carries, 440 yards and five TD’s. There’s a reason for that, and not just the shoulder.

Another reason.

Colts tried to draft his replacement

A year after investing the 143rd pick in the 2017 NFL Draft in Mack, and after watching him average 3.8 yards on 93 carries as a rookie (358 yards in 14 games), the Colts invested even higher in North Carolina State running back Nyheim Hines (104th overall) – and then drafted another running back with the 169th overall pick, Ole Miss’ Jordan Wilkins.

And Mack, well, he noticed.

“In this league, you know there’s competition,” Mack says. “You always hear: They’ll find the next guy to replace you. It is what it is. In this job, you can’t get upset by anything like that. You just got to go out and compete.”

The draft came two months after new Colts coach Frank Reich had given this tepid endorsement of Mack at the 2018 NFL Scouting Combine in Indianapolis:

“The evaluation process is ongoing as far as how he fits here,” Reich said.

Asked specifically if Mack is “a guy you think is capable of carrying the load,” Reich responded:

“We’ll have to evaluate that as we go.”

And it’s like I said: Mack noticed. He noticed all of it.

“Knowing Frank’s here now, and a bunch of new guys are coming in, you want to come in different,” Mack says. “Try to improve from last year.”

Different? Like this. Like against the Dolphins. First down at the Miami 14. Dolphins linebacker Kiko Alonso blitzes. He’s a split-second from Colts quarterback Andrew Luck when Mack slides over and flips Alonso upside down. The 6-3, 239-pound Alonso, the Dolphins’ leading tackler, lands on his head. Luck throws a 14-yard TD to Eric Ebron.

Those two areas – toughness and pass protection – are where Mack has improved the most. The big play? He had that in 2017, when 6.5 percent of his carries went at least 15 yards. His rate there is basically the same in 2018: 6.9 percent.

But it’s the dud plays, carries of zero or negative yards – plays where an NFL running back had better be able to run through Miami’s Reshad Jones or Dallas’ Chidobe Awuzie or Tennessee’s Harold Landry – where Mack has come the farthest. In 2017, damn near one-third of his carries (32.3 percent) resulted in zero yards or less. This season? He cut that number in half, to 16.4 percent, going from one of the worst rankings in 2017 (he was 74th of 75 NFL backs in this category) to well above average (27th of 72) in 2018.

That's the advanced statistic I was promising, but this one isn't bad: Last season Mack averaged 2.8 yards per carry between the tackles, according to research by IndyStar deputy sports editor Nat Newell. This season? Mack's up to 4.6.

Indianapolis Colts tight end Eric Ebron (85) reaches over the goal line for a touchdown as Houston Texans free safety Tyrann Mathieu (32) attempts to stop him in the first half of their AFC Wild Card playoff game at NRG Stadium in Houston, TX., on Saturday, Jan. 5, 2019. Matt Kryger/IndyStar

Indianapolis Colts tight end Eric Ebron (85) celebrates his touchdown in the first half of their AFC Wild Card playoff game at NRG Stadium in Houston, TX., on Saturday, Jan. 5, 2019. Matt Kryger/IndyStar

Indianapolis Colts cornerback Kenny Moore (23) and his teammates celebrate his interception in the first half of their AFC Wild Card playoff game at NRG Stadium in Houston, TX., on Saturday, Jan. 5, 2019. Matt Kryger/IndyStar

Indianapolis Colts cornerback Kenny Moore (23) and his teammates celebrate his interception in the first half of their AFC Wild Card playoff game at NRG Stadium in Houston, TX., on Saturday, Jan. 5, 2019. Matt Kryger/IndyStar

Indianapolis Colts tight end Eric Ebron (85) fights to control the ball but fails to come up with this touchdown catch during their AFC Wild Card playoff game at NRG Stadium in Houston, TX., on Saturday, Jan. 5, 2019. Matt Kryger/IndyStar

Indianapolis Colts tight end Eric Ebron (85) fights to control the ball but fails to come up with this touchdown catch during their AFC Wild Card playoff game at NRG Stadium in Houston, TX., on Saturday, Jan. 5, 2019. Matt Kryger/IndyStar

Indianapolis Colts strong safety Mike Mitchell (34) is helped off the field following an injury during their AFC Wild Card playoff game at NRG Stadium in Houston, TX., on Saturday, Jan. 5, 2019. The Indianapolis Colts defeated the Houston Texans 21-7 Matt Kryger/IndyStar

Indianapolis Colts tight end Eric Ebron (85) cradles the football like a baby following his touchdown during their AFC Wild Card playoff game at NRG Stadium in Houston, TX., on Saturday, Jan. 5, 2019. Ebron became a father for the second time earlier in the week. The Indianapolis Colts defeated the Houston Texans 21-7 Matt Kryger/IndyStar

Colts offensive coordinator Nick Sirianni and running backs coach Tom Rathman use the same word – “patient” – to describe one of the more underrated factors behind Mack’s improved running. Coach Frank Reich cites pass protection when he says, “Marlon has proven to me … you can put (him) in at any down, in any situation, and he is ready to go.”

And I’ll just leave you with one more statistic, as the Colts prepare for a NFL Divisional Round playoff game Sunday at the Kansas City Chiefs:

Mack has missed four games this season with a variety of ailments (hamstring, ankle, foot, concussion), the by-product of playing a violent position in a violent sport. In those four games, the Colts are 0-4.